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Maintaining Permeable Pavements
INTENDED FUNCTION AND BENEFITS OF MAINTENANCE
Research studies and anecdotal case stud­ies from across the USA and the world have shown that permeable pavements substantially and significantly reduce runoff volumes, limit peak flows, and sequester (trap) many types of pollut­ants. Many permeable pavements further improve ground water recharge, have high albedo (light reflectivity), reduce runoff temperature, and improve aesthetics. Permeable pavements are able to achieve this by allowing water to pass through the surface layer and temporarily collect in underlying aggregate storage layers. This water then either is released back to the storm drain system through underdrains or infiltrates into the underlying soil, or a combination of both. A small fraction of runoff will evaporate or evapotranspire. To enable permeable pavements to func­tion as intended, however, inspection and consequent maintenance are imperative.
TYPES OF PERMEABLE PAVEMENTS
For the purposes of this bulletin, any pavement that is intended to let water pass through its surface and temporarily collect in an underlying aggregate storage zone is termed permeable pavement. However, among this broad definition of pavement, there are several specific types. Several of these types are pictured in Figure 1 below. For specific details of each pavement type, please see AG-588-14W (Permeable Pavement: Research Update and Design Implications).
Permeable concrete (PC) is a mix­ture of Portland cement, fly ash, washed gravel, and water. Permeable asphalt (PA) consists of fine and course aggregate stone bound by a bituminous-based binder. Water
Figure 1. Types of permeable pavement. Top L-R: Permeable concrete (PC), permeable asphalt (PA), permeable interlocking concrete pavers (PICP). Bottom L-R: concrete grid pavers (CGP), plastic rein­forcing grids (PG) filled with gravel, and PG with grass.

Maintaining Permeable Pavements
INTENDED FUNCTION AND BENEFITS OF MAINTENANCE
Research studies and anecdotal case stud­ies from across the USA and the world have shown that permeable pavements substantially and significantly reduce runoff volumes, limit peak flows, and sequester (trap) many types of pollut­ants. Many permeable pavements further improve ground water recharge, have high albedo (light reflectivity), reduce runoff temperature, and improve aesthetics. Permeable pavements are able to achieve this by allowing water to pass through the surface layer and temporarily collect in underlying aggregate storage layers. This water then either is released back to the storm drain system through underdrains or infiltrates into the underlying soil, or a combination of both. A small fraction of runoff will evaporate or evapotranspire. To enable permeable pavements to func­tion as intended, however, inspection and consequent maintenance are imperative.
TYPES OF PERMEABLE PAVEMENTS
For the purposes of this bulletin, any pavement that is intended to let water pass through its surface and temporarily collect in an underlying aggregate storage zone is termed permeable pavement. However, among this broad definition of pavement, there are several specific types. Several of these types are pictured in Figure 1 below. For specific details of each pavement type, please see AG-588-14W (Permeable Pavement: Research Update and Design Implications).
Permeable concrete (PC) is a mix­ture of Portland cement, fly ash, washed gravel, and water. Permeable asphalt (PA) consists of fine and course aggregate stone bound by a bituminous-based binder. Water
Figure 1. Types of permeable pavement. Top L-R: Permeable concrete (PC), permeable asphalt (PA), permeable interlocking concrete pavers (PICP). Bottom L-R: concrete grid pavers (CGP), plastic rein­forcing grids (PG) filled with gravel, and PG with grass.